Carburetor



Fell 20, 1934-` A. M. PREN-rls's CARBURETOR Filled Feb. 1, 1932.

llllllillll/Il and' Q 97 ATTORNEY Patented Feb. 20, 1934 UNITED STATES PATENT OFFICE CARBURETOR Application February 1,

16 Claims.

shown in my copending application cited, with- K out a special acceleration device, gives greatly superior acceleration performance over prior art suction-feed carburetors with acceleration devices, I nd that still better performance can be secured from my pressure-feed carburetor when same is provided with my improved acceleration device, as herein disclosed, especially as regards regulation of the accelerating charge to variations in temperature.

An object of this invention is to provide a carburetor of the pressure-feed ,type wherein the normal liquid fuel supply is temporarily augmented when the throttle is suddently opened so as to still further facilitate acceleration of the engine.

Another object of this invention is to provide a carburetor of the pressure-feed type wherein the additional supply of liquid for acceleration is regulated in accordance with the temperature of the carburetor so that, as this temperature increases, thelacceleration fuel supply decreases.

Still another object of this invention is to provide a carburetor of the pressure-feed type wherein the acceleration device supplies additional compressed air as well as liquid fuel to the mixing chamber when the throttle is suddenly opened. 4

A still further object of my invention is to provide a carburetor of the pressure-feed type wherein the accelerating device is mechanically operated by the throttle.

With these and other objects in View which may be incident to my improvements, my invention consists of the combination and arrangement of elements hereinafter described and illustrated in the accompanying drawing which shows in central longitudinal section, a carburetor embodying my improvements.

Referring to the drawing, the reference numeral 1 denotes the body of a carburetor having a main air intake 2, Venturi throat 3, mixing chamber 4, and mixture outlet 5 controlled by a butterfly throttle valve 6 mounted upon a 1932. Serial No. 590,294

shaft 7 journalled in the walls of the mixture outlet.

Integral with the bottom Wall of air intake passage 2 is a main jet nozzle which rises to a point just above the center of throat 3 and consists of an outer liquid fuel tube 8 and a concentric inner compressed air tube 9. Tube 8 is surmounted by an adjustable screw-threaded cap 10 having a central aperture 11, through which the compressed air and liquid fuel issue in the form of a "highly atomized spray.

It will be appreciated that the relative positions of the air and liquid fuel tubes may be reversed without apprecably affecting the functioning of the main jet nozzle, or departing from the spirit of my invention.

Liquid fuel tube 8 communicates through a passageway l2 and port 13 with a liquid fuel reservoir 14 into which liquid fuel under superatmospheric pressure enters through inlet 15 controlled by a valve 16 which is actuated by a float 17 to maintain the liquid fuel at a normal level X-X, in the usual manner. The normal flow of liquid fuel from reservoir 14 to tube 8 is controlled by a manually adjustable valve 18 which regulates the free opening through port 13. Air tube 9 communicates through an air passageway 19 and metering restriction 19a to a second air passageway 20 which in turn communicates through a compressed air supply pipe 21 with an air pump (not shown).

A slight superatmospheric air pressure is maintained in reservoir 14 during the operation of the carburetor by means of a metering restriction 22, which admits compressed air into reservoir 14 from air passage 20, and a second smaller metering restriction 23 which permits compressed air to escape from reservoir 14 into the atmosphere at such a controlled rate as will maintain the desired pressure in reservoir 14.

Integrally attached to the bottom Wall of reservoir 14 is a cylinder 24 which is divided by a transverse wall 25 into an upper chamber 26 and a lower chamber 27. Chamber 26 communicates through a pipe 28, passageway 29, and port 30 with mixing chamber 4 and through a series of ports 31 with reservoir 14. Adapted to reciprocate Within chamber 26,A with an air-tight t is a piston 32 having adjustably attached thereto a piston rod 33 which passes through a liquidtight stung-box 34 in wall 25 and is similarly attached by screw threads to a sleeve valve 35, adapted to reciprocate in chamber 27 also with an air-tight fit. Interposed between piston 32 and the top of chamber 26 is a helical spring 36 which is arranged to force piston 32 down in opposition to the action of the vacuum in mixing chamber 4 which is transmitted to chamber 26 through passage 29 and pipe 28.

Integrally attached and depending from the bottom wall of reservoir 14 is a Valve chamber 37 which is of the same bore as chamber 27,`

so that sleeve valve 35 slides therein with an air-tight t. Valve chamber 37 communicates with air passage 20 through a generally triangular shaped port 38 which admits compressed air into chamber 37 whenever valve 35 is raised and uncovers a part of said port. The shape of port 39 is not truly triangular but the sides thereof are curvedy so that the area uncovered by valve 35 at any given position is sufficient to pass the exact quantity of air required to form a mixture of desired proportions, under the degree of vacuum existing in the mixing chamber 4 at the time. Chamber 37 communicates with mixing chamber 4 by means of connecting passageways 39, 40, 41 and 42, and a slot-shaped port 43 in sleeve valve 35, the width of which port is equal to the diameters of passageways and 20.

Communicating with liquid fuel tube 8 through a passageway 44 and with air tube 9 through a passageway 45 is an acceleration pump chamber 46 in which a piston 47 reciprocates with an air-tight fit. Attached to piston 47, by adjustable threaded lock nuts 48, is a piston rod 49 which extends up through an aperture 50 in cover 51 of chamber 46 and is engaged by a concentric helical spring 52 interposed between the cover 51 and a washer 53 adjustably held in place on rod 49 by a threaded nut 54. The free end of rod 49 is bent at a right angle and engages a slot 55 in the end of a lever 56 which is pivoted at 57 to the wall of mixing chamber 4 as shown in the drawing.

Fixedly secured to throttle shaft 7 is an eccentric cam` 58 which is adapted to bear upon lever 56 and depress it whenever throttle 6 is opened by movement of operating lever 59 xed to shaft 7 and connected to the accelerator pedal y of the car (not shown). The throw of cam 58 is such that, through lever 56 and rod 49, piston 47 is caused to make a predetermined stroke in cylinder 46, and whenever cam 58 is returned to its horizontal position, as shown in the drawing, spring 52 returns piston 47 to the top of its stroke. Air is admitted into chamber 46 through aperture 50 and passes downwardly through a port 60 in piston 47 but is prevented from passing upwardly through said piston by a ap check valve 61 which is pivoted to piston 47 and held normally closed by a leaf spring 62.

Air passage 45 is normally closed by a spring pressed check valve 63 positioned near the upper end of said passage which terminates just above the static liquid fuel level line X-X.

The ow of liquid fuel throughpassage 44 is regulated by a thermally responsive valve 64 which is actuated by a thermostatic element 65 adjustably secured to valve 64 by a pair of threaded lock nuts 66. Thermostatic element 65 is fixed to the wall of passage 44 by a plurality of screws 67.

From the construction described above, it is apparent that whenever the carburetor is not in operation (engine at rest), liquid fuel will enter chamber 46 through tube 8 and passageway 45 and stand therein at the same level X-X as in reservoir 14, since piston 47 will a1- ways be at the top of its stroke under this condition. When the carburetor is in operation, the superatmospheric pressure in reservoir 14 forces the liquid fuel up into chamber 46 until the air entrapped under piston 47 is compressed lto a point where it equals the air pressure in reservoir 14.

Valve 63 is set to open when the pressure in chamber 46 equals or exceeds the pressure in the air line 19 and 9. A check valve 68 in passageway 12 prevents the return of fuel to reservoir 14 when piston 47 creates a greater pressure in liquid fuel passageways 45 and 8 than the normal pressure maintained in reservoir 14, so that the liquid fuel expelled from chamber 46 must discharge out through aperture 11 into mixing chamber 4.

The operation of my device is as follows. When the engine is at rest the throttle is in its most restricted position, as shown in the drawing, and liquid fuel stands in reservoir 14, tube 8, and chamber 46 at the static level line X-X.

When the engine is started, the throttle 6 is cracked, but the shape of cam 58 is such that this slight opening of the throttle does not move piston 47. Compressed air now enters reservoir 14 and is maintained therein at a substantially constant superatmospheric pressure, slightly below that in air line 19 and 9, as long as the engine is running. This air pressure in reservoir 14 tends to force the liquid in chamber 46 above the level X-X, but as this pressure is slight (say about one pound per square inch, gauge) only a small rise in the liquid level in chamber 46 takes place as the air in said chamber is compressed thereby and soon rises to an equal pressure and checks the further rise of the liquid level. Any further rise in the pressure of the air in chamber 46, as would be caused by a downward movement of piston 47 immediately unseats valve 63 and opens air passage 45. This is the normal action when piston 47 descends slowly as when throttle 6 is opened slowly, and under these conditions, as the pressure on the liquid fuel in chamber 46 is approximately equal to that in tube 8, there is no appreciable discharge of liquid fuel from chamber 46. If, however, piston 47 descends rapidly (as when throttle 6 is suddenly opened) the air pressure in chamber 47 rises above that in air tube 9, since passage 45 is relatively very small so that the air in chamber 46 cannot escape therethrough fast enough to prevent a higher pressure being developed by piston 47. This superior pressure at once forces the liquid fuel out of chamber 46 through passageway 44 into tube 8 where it augments the normal flow through tube 8 and issues as an increased flow from aperture 11.

As soon as piston 47 stops on its downward stroke, there is no further compression of the air in chamber 46, `but the air already compressed lcontinues to discharge through passage 45 and to force fuel out through passage 46 until the air pressure in chamber 46 drops to a value equal tothat in air tube 9, whereupon valve 63 seats and closes passage 45 and the pressure on the liquid fuel in chamber 46 equalizes with that in tubeA 8 and no further discharge takes place from chamber 46. By this arrangement it is to be particularly noted that the acceleration pump during operation not only supplements the feed of liquid fuel but also the feed of vcompressed air through `the main jet nozzle.

When the throttle 6 is closed, spring 52 returns` piston 47 to its uppermost position and causes lever 56 t'o always bear against cam 58. When piston 47 rises on its return stroke, air trapped in chamber 46 above the piston, cannot escape fast enough through aperture 50, and therefore flows into the space below the piston through port 60. At the same time the pressure in chamber 46 below the piston is reduced by the upward movement of piston 47 and this permits liquid fuel to reenter through passage 44 under the superatmospheric pressure in reservoir 14.

The foregoing operation has been without regard to temperature. In order to regulate the accelerating charge so that it will bear an 'inverse proportion to the carburetor temperature, I have provided a valve 64 which is operated by a thermostatic element 65 so arranged and calibrated that valve 64 fully opens passage 44 only at the lowest operating temperatures of the carburetor and completely closes this passageway at the highest operating temperature of the carburetor. Between these temperatures the degree of opening is inversely proportional to the temperature so that as the temperature rises the acceleration charge is correspondingly reduced, as is desirable for best operation of the engine.

While I have shown and described the preferred embodiment of my invention, I desire it to be understood that I do not limit myself to the precise details of construction shown by way of illustration, as these may be changed and modified in combination and arrangement by those skilled in the art without departing from the spirit of my invention or exceeding th scope of the appended claims'.

I claim:

1. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, and means for feeding into said chamber liquid fuel from said reservoir under a continuous superatmospheric air pressure, means for feeding compressed air to said reservoir, andnneans actuated by said,throttle for temporarily increasing said pressure when said throttle is suddenly opened whereby said liquid fuel feed is temporarily increased at the same time.

2. In a carburetor having athrottle, a mixing chamber, a liquid fuel reservoir, means for supplying said chamber with liquid fuel from said reservoir and air under a continuous superatmospheric pressure, means for feeding compressed air to said reservoir, and means actuated by said throttle for temporarily increasingsaid liquid fuel and air supplies when said throttle is suddenly opened.

3. In a carburetor having a throttle, a mixing chamber, a Iliquid fuel reservoir, and means for feeding into said chamber liquid fuel from said reservoir and air each under a continuous superatmospheric pressure, means for feeding compressed air to said reservoir, and means actuated by said throttle for temporarily increasingsaid pressure when said throttle is suddenly opened whereby said liquid fuel and air feeds are temporarily increased at the same time.

4. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, means for supplying said chamber with liquid fuel from said reservoir under a continuous superatmospheric air pressure, means for feeding compressed air to said reservoir, and temperature regulated means including a piston actuated by o said throttle for temporarily increasing said liquid fuel supply when said throttle is suddenly opened.

5. In a carburetor having a throttle, a mixing chamber, `a liquid fuel reservoir, and means for feeding into said chamber liquid fuel from said reservoir under a continuous superatmospheric air pressure means for feeding compressed air to said reservoir, and temperature regulated means including a piston actuated by said throttle for temporarily increasing said pressure when said throttle is suddenly opened whereby said liquid fuel feed is temporarily increased at the same time.

6. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, means Yfor supplying said chamber with liquid fuel from said reservoir under a continuous superatmospheric air pressure means for feeding compressed air to said reservoir, and means actuated by said throttle for temporarily increasing said liquid fuel supply when said throttle is suddenly opened, and means for regulating said temporary increase of fuel supply in accordance with the temperature of the carburetor.

7. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, means for supplying sa'd chamber with liquid fuel from said reservoir and air each under a continuous superatmospheric air pressure means for feeding compressed air to said reservoir, and means actuated by said throttle for temporarily increasing said liqud fuel and air supplies when said throttle is suddenly opened, and means for regulating said temporary increase of fuel supply in accordance with the temperature of the carburetor.

8. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, and means for feeding into said chamber liquid fuel from said reservoir under a continuous superatmospheric air pressure means for feeding compressed air to said reservoir, and means actuated by said throttle vfor temporarily increasing said pressure when said throttle is suddenly opened whereby said liquid fuel feed is temporarily increased at. the same time, and means for regulating said temporary increase of fuel feed in accordance with the temperature of the carburetor.

9. In a carburetor having a throttle, a mixing chamber, a liquid fuel reservoir, and means for feeding into said chamber liquid fuel from said reservoir and air each under a continuous superatmospheric pressure means for feeding compressed air to said reservoir, and means actuated by said throttle for temporarily increasing said pressure when said throttle .is suddenly opened whereby said liquid fuel and air feeds are temporarilyincreased at the same time, and means to vary said temporary increase of fuel feed inversely as the temperature of the carburetor.

10. In a carburetor having a throttle, a mixing chamber, an acceleration pump comprising a piston actuated by said throttle, a cylinder,

air under a continuous superatmospheric air pressure to said cylinder below said piston.

12. In a carburetor having a mixing chamber, an acceleration pump comprising a cylinder communicating with said chamber, and means to supply liquid fuel and air both under superatmospheric pressure from said cylinder in said chamber.

13. In a carburetor having a mixing chamber, an acceleration pump comprising a pump cylinder communicating with said chamber, and means to supply liquid fuel and air each under a superatmospheric air pressure to said cylinder, means to increase the pressure in `said cylinder, and means to discharge said fuel into said chamber under said increased pressure.

14. In a carburetor having a mixing chamber, an acceleration pump comprising a cylinder communicating with said chamber, and means to supply liquid fuel and air both under'superatmospheric pressures to said cylinder, means to increase the pressure in said cylinder, and means to discharge said fuel and air into said chamber under said increased pressure.

15. In a carburetor having a mixing chamber, a oat reservoir, an acceleration pump comprising a pump cylinder communicating with 

